The Defense Department said the soldiers were killed in an airstrike Monday during a battle with enemy forces in Zabul Province, which borders Pakistan's tribal areas.

The Pentagon said the incident is under investigation.

"We do have reason to suspect that friendly fire was the cause," Pentagon press secretary Rear Adm. John Kirby said last week. An Afghan soldier and an interpreter also were killed, Afghan authorities said.

McDonald was assigned to the first Battalion, Fifth Special Forces Group at Fort Campbell Kentucky.

The Army said the other four soldiers are Army Staff Sgt. Scott Studenmund, 24, of Pasadena, Calif.; Justin Clouse, 22, of Sprague, Wash.; Justin Helton, 25, of Beaver, Ohio; and Aaron Toppen, 19, of Mokena, Ill.

McDonald's aunt, Kathy Harris says McDonald was someone who could always make you laugh. He went to high school in Cordele, and signed up for the Army shortly afterwards in 2004.

He had done several tours in Afghanistan and Iraq over his 10 year military career. He leaves behind a wife and two daughters in Tennessee.

The family says his funeral will like be held at Arlington National Cemetery, but a date has not been set yet.